Historically, highly branched alkylbenzenesulfonate surfactants, such as those based on tetrapropylene (known as “ABS” or “TPBS”) were used in detergents. However, these were found to be very poorly biodegradable. A long period followed of improving manufacturing processes for alkylbenzenesulfonates, making them as linear as practically possible (“LAS”). The overwhelming part of a large art of linear alkylbenzenesulfonate surfactant manufacture is directed to this objective. Large-scale commercial alkylbenzenesulfonate processes in use in the U.S. today are directed to linear alkylbenzenesulfonates. However, linear alkylbenzenesulfonates are not without limitations; for example, they would be more desirable if improved for hard water cleaning properties.
In the petroleum industry, various processes have recently been developed, for example for producing low viscosity lube oil or high-octane gasoline, which the inventors have now found provide useful new insight on how to delinearize hydrocarbons to a limited and controlled extent. Such deliberate delinearization, however, is not a feature of any current commercial processes in the different field of alkylbenzenesulfonate surfactant manufacture for consumer products. This is not surprising, in view of the overwhelming volume of LAS surfactant art teaching toward making linear compounds and away from delinearization.
The majority of commercial processes for making alkylbenzenes rely on H or aluminum chloride catalyzed alkylation of benzene. Quite recently, it has been discovered that certain zeolite catalysts can be used for alkylation of benzene with olefins. Such a process step has been described in the context of otherwise conventional processes for manufacture of linear alkylbenzenesulfonates. For example, the DETAL® process of UOP uses a zeolite alklylation catalyst. The DETAL® process and all other current commercial processes for alkylbenzenesulfonate manufacture are believed to fail to meet the internal isomer selectivity requirements of the preferred inventive process and alkylation catalyst defined hereinafter. Moreover, the DETAL® process catalyst or catalysts are believed to lack the moderate acidity and intermediate pore size of alkylation catalysts used in the preferred processes of the present invention. Other recent literature describes the use of mordenite as an alkylation catalyst, but no such disclosure makes the combination of specific process steps required by the instant invention. Moreover, in view of the linearity desired in alkylbenzenesulfonate products of conventionally known processes, they also generally include steps directed to the provision or making of a substantially linear hydrocarbon, not a delinearized one, prior to the alkylation. Possible exceptions are in U.S. Pat. No. 5,026,933 and U.S. Pat. No. 4,990,718. These and other known processes have numerous shortcomings from the standpoint of the detergent industry in terms of cost, catalyst limitations in the propylene oligomerization or olefin dimerization stage, presence of large volumes of distillation fractions that would need to be discarded or find non-detergent customers, and limited range of product compositions, including mixtures of chainlengths attainable. Such developments by the petroleum industry are, in short, not optimal from the standpoint of the expert formulator of detergent products.
It is also known in the art how to make linear alkylbenzenes using particular adsorptive separation processes. See U.S. Pat. No. 2,985,589. Such processes as described hitherto however do not provide branched alkylbenzenesulfonates.
It is also known in the art to prepare long-chained methyl paraffins for use as industrial solvents by processes which include urea clathration and separation on “molecular sieves”. See Chemical Abstracts, 83:100693 and JP 49046124 B4. This process assertedly involves double urea adduction, for example treating a petroleum fraction once with urea to remove n-alkanes as complexes, and then a second time with excess urea to obtain adducts of mixed n-alkanes and long-chained monomethyl paraffins. While this process may have some limited usefulness and may be included in the overall processes of the invention as most broadly defined, its limitations are considerable. This process, despite dating from 1974, is not known to have been incorporated into any overall process for making surfactants such as the modified alkylbenzenesulfonates described herein.
As further described in the Background Art section hereinafter, it is also known how to make various OXO alcohols and to make surfactants therefrom. However, the currently available OXO alcohols have shortcomings, such as in producing surfactants which are less soluble at a given chainlength than might be desired for the increasingly popular low wash temperatures or in relying on relatively expensive processes such as olefin oligomerization, isomerization and disproportionation; or in still having a relatively high content of linear material.